Very blue light traveling FAST from north to south high in the sky.I was driving home on a dark street with very few street lights. Just before driving over the hill moments before pulling into my drive way I thought I saw a blue light to my left high in the sky but I let it go thinking it was the reflection of the firehouse lights I passed on the power lines.Seconds later I realized there really was a light in the sky. It was moving incredibly fast and it was a blue light that wasn't blinking. It looked very high in the sky but it was easy to see.It moved smoothly from the left part of the sky to the right part of the sky and there as no sound. It took about several seconds to cross over to the other side. It was coming from the south going directly north. I live along the Hudson River and the town is very dark so the sky is usually very visible on a clear night.